Control system for bridge-type phase-splitters.



. M. HARTENHEIM.

' CONTROL SYSTEM FOR BRIDGE T YPE PHASE SPLITTERS.

APPLICATION FILED FEB. 10. l9l6- RE NEWEP MAY 13. 19 18.

Patented Nov. 12, 1918.,

WITNESSES: 224d M M INVENTOR Ala/r A a'rfm/w/m ATTORNEY MAX HARTENHEIM,0F IITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC ANDMANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

conraor. SYSTEM FOR BRIDGE-TYPE rnasnsrurrnns.

Specification of Letters Patent.

Patented Nov. 12, 1918.

Application filed February 10, 1916, Serial No. 77,404. Renewed May 13,1918. Serial No. 234,308.

To all whom it may concern:

Be it known that I, MAX HARTENHEIM, a subject of the Emperor of Germany,and a resident of Pittsbur h, in the county of Allegheny and State 0Pennsylvania, have invented a new and useful Improvement in ControlSystems for Bridge-Type Phase- Splitters, of which the following is aspecification.

My invention relates to alternating-current distributing systems andespecially to control systems for polyphase apparatus, such as motors,generators, rotary converters,'and the like that may operate onsinglephase circuits through the intermediary of phase-splittingdevices.

More particularly, my invention relates to means associated with analternating-current system of the above indicated character whereby thevoltage impressed upon the'terminals of the aforesaid polyphaseapparatus may be maintained balanced and equal irrespective of the loadsimposed thereupon.

It is well known that when four elements of equal reactance, two beingcondensive and two being inductive, are connected'in a closed circuit soas to alternate in position with one another, and an alternating-currentvoltage of the proper frequency is impressed across two opposite pointsof the closed circuit, a current of constant value may be obtained in acircuit that is connected across the other two opposite points of theclosed circuit. This system'of connection has been designated amono-cyclic square in which the current flowing in the constant-currentcircuit is maintained, under certain conditions, 90 degrees out of phaserelationship with the constant voltage impressed upon the square by theconstant-potential circuit.

It is proposed to modify the aforementioned mono-cyclic squarearrangement in order to utilize the same as a phase-splitting devicewhereby a polyphase motor, generator, rotary converter and the like, maybe operated from a single-phase circuit by reason of the phasemodification eifected by a modified arrangement of the mono-cyclicsquare which I will designate as a bridge. In this bridge arrangement,the several reactances are so adjusted that, when a voltage of a certainpredetermined frequency is impressed across one diagonal of the bridge,an equal voltage of the same frequency may be obtained from the otherdiagonal of the bridge, said second voltage being displaced h load ismaintained at a predetermined value.

The reactances of the bridge are consequently selected in accordancewith the phase-currents necessary for sustaining this predeterminedload.

As the load upon the motor varies, resul ing in a change in the currentor currents supplied thereto, the voltage impressed across the bridgephase of the motor will change likewise, causing an abnormal differenceof potential to exist across the corresponding diagonal of the bridge.The balance of the voltages impressed upon the several phases of themotor will be consequently disturbed which results from thisdistortionof the voltage, both in value and phase relationship, that is impressedacross one of the two diagonals of the brid e. If the distortion' in thevoltages is suficient, as a consequence of the unequal currents flowingin the several phases of the motor, the potential difference across onediagonal of the bridge may be sufficient to destroy the insulatingproperties of the reactance elements comprising the bridge.

In order to, maintain a balanced condition between the voltagesimpressed upon the several phases of the apparatus through theintermediary of the bridge arrangement, under all load conditions, it isnecessary to maintain the potentials of the four corners of the bridgeequal, and this may be effected if the values of the capacity reactanceelements are varied in direct proportion to the current supplied tothebridge-fed phase of the motor, while the values of the inductanceelements, at the same time, are Varied in inverse proportion thereto. Toautomatically effect this control of the values of the reactanceelements comprising a bridge arrangement of the aforementioned characterirrespective of the load conditions imposed upon the polyphaseapparatus,I have invented the control system herein shown and described,

by means of which the voltages impressed upon the several phases may beautomatically maintained balanced.

For a better understanding of the scope of my invention, reference maybe had to the a secondary winding 5 thereof being con-- nected acrossone diagonal of the bridge 2 to the corners 6 and 7, substantially asshown. At the same time, a phase 8 of the polyphase motor 1 is connectedto the corners 6 and 7, thereby being directly supplied from thesingle-phase circuit 3.

, able inductive reactance elements 11 and '12,

the elements having difierent characteristics alternating in position,as shown, to form a closed circuit. Another phase 13 of the motor 1 isconnected to corners 14 and 15 of another diagonalof the bridge 2. Aseries transformer 16'has a primary winding 17 connected in circuit withthe bridge-phase 13 of the motor 1 and a secondary winding 18 connectedto a coil 19 of an electromagnet 20 that comprises a core 21, an uppersupporting member 22 and a lower supporting member 23. The members 22and 23 are of similar construction but inverted in position, and eachcomprises a plurality of conducting bridging members 24 which slidinglyengage rods 25. The several bridgmg members 24 mounted upon the rods 25are spaced unequaldistances from one another when the supports 22 and 23are in their normal positions, as shown. The distance between thecontact members 24 may be varied, however, by compressing spring members26, which extend between adjacent members 24. The aforementionedarrangement permits the bridging members 24 to engage correspondingcontact members 27 in succession as the core member 21 is drawn upwardlyan increasing distance by the electromagnet 20.

We will assume that, under normal load conditions of the motor 1, thebridge 2 main-- tains the voltages impressed upon the several phases ofthe motor 1 balanced, that is,

equal in value to, and displaced 90 degrees in phase relationship from,each other; As the load upon the motor 1 increases, the currentsdelivered to the several phases thereof must necessarily increase invalue. As mentioned above, the variation in the current supplied to thebridge-fed phase 13 of the motor 1 will efi'ect a distortion in thepotential differences existing between the diagonally opposite corners14 and 15 of the bridge2, which disturbs the balanced relationshipbetween the voltages applied to the several phases of the motor 1. Itis, therefore, necessary, as explainedabove, to automatically controlthe values of the different reactance elements of the bridge in order tomaintain balanced voltage conditions. This automatic regulation iseffected through the electromagnet 20 which re sponds to the currentflow through the serles transformer 16 that is inserted in the bridgefedphase of the motor. For a certain predetermined current variation fromnormal, the core 21 will be drawn upwardly a sufficirnt amount to efiectengagement between the contact members 27 and the bridging member 24*,and the contact members 27 and the bridging member 24". It will be notedthat both the supports 22 and 23 will be simultaneously actuated toeffect corresponding changes 'in the four elements of the bridge. Inthis instance, sections 28 and 28 of the inductivereactance elements 11and 12, respectively, are simultaneously cut out of circuit, andcondensers 29 and 29 are simultaneously cut into circuit, the values ofthe condensive reactance elements 29 and 29 being directly proportionalto the current variations in the bride-fed phase of the motor, and thevalues of the'inductive reactance elements 28and 28 being inverselyproportional to the same current variation. In other words, thebalancing of the bridge is not disturbed, since corresponding amounts ofcapacity reactance are inserted in two opposite arms of the bridge whilecorresponding amounts of inductivereactance are disconnected from theother two arms of the bridge. 'Of coures, the values of "the differentelements to be disconnected and connected in their respective arms ofthe bridge 2 must be so determined as to maintain balanced voltagesacross the two diagonals of the bridge. This is easily determinedbecause of the aforesaid relationship existing between the severalelements comprising the bridge. If the current delivered to thebridge-fed phase 13 of the motor 1 tends to increase further, the coremember 21 will be drawn upwardly a greater distance, therebydisconnecting more and more of the inductive reactance elements 11 and12- from the bridge circuit and inserting more and more capacityreactance in the arms 9. and 10 of the bridge. The structure shownprovides for four variations to be effected as the current in thebridgefed phase of the motor decreases through a certain predeterminedrange.

It will be appreciated that the tuning of the bridge; that is, theresonant frequency, will not be disturbed by varying the values of thecapacity and inductive reactances of and 14 is exactly equal to, anddisplaced 180 degrees in phase relationship from, the voltage impressedacross the corners 7 and 15. Similarly, the voltage impressed across thecorners 6 and 14 for the same frequency is exactly equal to, anddisplaced 180 degrees in phase relationship from, the voltage impressedacross the corners 6 and 15. By varying the values of the reactance andcondensive elements, as above mentioned, these resonant conditions aremaintained irrespective of the current supplied to the bridge-fed phaseof the motor 13, within a limited range. Moreover, the voltagesimpressed across the phases 8 and 13 will, under all conditions of load,be maintained equal to, and displaced 90 degrees in phase relationshipfrom, each other, thereby permitting the motor 1 to be operated underbalanced conditions as a two-phase motor irrespective of the loadsimposed thereupon.

While the above description mentions only single-phase and two-phasecircuits, it is not to be understood that this imposes a limitation and,furthermore, I do not intend to limit my invention to distributingsystems in which the two-phase or polyphase circuits are supplied withower from the singlephase circuit, since e polyphase circuit may be thesource of power supply while the single-phase circult constitutes thepowerconsuming circuit.

While I have shown and described one embodiment of my invention, it willbe understood thatmany modifications may be made therein withoutdeparting from the spirit and scope of the appended claims.

I claim as my invention:

1. The combination with a single-phase circuit and a polyphase circuit,of a phasesplitting device comprising static reactive elements only forinterconnecting said circuits with each other, and means influenced bythe current flow in one of the phases of said polyphase circuit forautomatically adjusting the phase-splitting device to maintain balancedconditions in the polyphase circuit.

2. The combination with a single-phase circuit and a polyphase circuit,of a phasesplitting bridge comprising inductive and condensive reactanceelements alternating in position with one another in a closed circuitfor interconnecting said circuits with each other, and means forautomatically varying the values of said reactance elements inaccordance with the current flowing in one of the phases of thepolyphase circuit.

3. The combination with a single-phase circuit and a polyphase circuit,of a phase splitting bridge comprising inductive and condensivereactance elements alternating in position with one another in a closedcircuit for interconnecting said circuits with each other, and means forautomatically varying the values of said condensive reactance elementsand inductive reactance elements, respectively, in direct proportion andin inverse proportion to the current flow in one of the phases of thepolyphase circuit.

4. The combination with a single-phase circuit and a polyphase circuit,of a phasespiitting bridge comprising adjustable inductive andcondensive reactance elements alternating in position with one anotherin a closed circuit for interconnecting said circuits with each other,and an electromagnet excited in accordance with the current flowobtaining in one phase of said polyphase circuit for automaticallyvarying the condensive and inductive admittances of said phasesplittingbridge in proportion to the currents obtaining in the polyphase circuit.

5. The combination with a single-phase circuit and a polyphase circuit,of a phasesplitting bridge comprising adjustable inductive andcondensive reactance elementsalternating in position with one another ina closed circuit for interconnecting said circuits with each other, andmeans for varying the condensive and inductive admittances withoutvarying the product of said admittances of the phase-splitting bridge inaccordance with the current flow obtaining in the phase derived fromsaid bridge.

In testimony whereof, I have hereunto subscribed my name this 4th day ofFeb, 1916.

. MAX HARTENHEIM.

